The present invention relates generally to safety devices to protect occupants of moving vehicles. More particularly, the present invention relates to an opening device for a cold gas inflator.
It is well known in various technologies to require the rapid release of pressurized fluid from a pressure vessel. Examples of such technologies include vehicle occupant inflatable restraints, fire suppression systems, and emergency air containers.
In the field of vehicle occupant inflatable restraints, the cold gas inflator inflates a vehicle airbag by releasing stored gas. The stored gas generally comprises one or more inert gases such as argon or helium, and in the event of an automobile crash, the stored gas exits the cold gas inflator and flows into an airbag, which causes the airbag to inflate. Since cold gas inflators release stored gas, these inflators do not have the problems typically associated with other types of inflators such as toxic gas and hot inflation gas.
Cold gas inflators are suitable for use in inflating curtain, thorax, and head and thorax airbags. Curtain airbags are mounted in the roof of a vehicle and when inflated, protect the occupant""s head. Thorax airbags are mounted lower than curtain airbags and are generally mounted in vehicle seats.
Cold gas inflators are equipped with a discharge opening, and the stored gas must travel through this passageway to exit the pressure vessel. Typically, the discharge opening has a blocking member, which prevents the stored gas from passing through the discharge opening and escaping the pressure vessel. During an automobile crash, an opening device must quickly remove the blocking to allow the airbag to be rapidly deployed. It is paramount that the opening device be reliable so that the actuation of an opening device always yields an unblocked discharge opening. Along with being reliable, it is desirable for the opening device to be made from as few parts as possible. An example of an opening device operates by removing a support for a sealing element. Once the sealing element loses its support, the sealing element ceases to block the discharge opening and the stored gas is able to flow through the discharge opening. This type of opening device is known from U.S. Pat. No. 6,247,725 B1. Another type of opening device works by generating a shock wave. The inflator in WO 01/42047 A2 uses a shock wave to open a burst disc, which causes the stored gas to escape from the gas vessel. The inflator in U.S. Pat. No. 5,022,674 also uses a shock wave to break the disk permitting inflation gas to exit the pressure vessel.
In the present invention, the cold gas inflator includes an opening device for unblocking the discharge opening. The discharge opening is blocked with a burst disk, and the burst disk has a dome-shape configuration when the pressure vessel is filled with stored gas. The opening device for the present invention is an igniter with an ignition material and a nozzle, which both retains the igniter to the igniter endcap and also focuses the output energy of the igniter greatly increasing the reliable opening of the burst disc. Actuation of the igniter results in the generation of a shock wave, which has enough energy to fully rupture the burst disk. Once the burst disk has been ruptured, the stored gas is not obstructed by the burst disk and is able to leave the inflator by flowing through the discharge opening.
According to one aspect of the invention, the cold gas inflator is provided with an orifice plate to restrict the flow of stored gas through the discharge opening.
Another aspect of the invention includes an axial flow diffuser to direct the stored gas out of the cold gas inflator in an axial direction as oppose to a radial direction. In this embodiment, the gas flows away from the inflator along the longitudinal axis of the inflator. In this embodiment, the acute angle formed between the longitudinal axis of the opening device and the longitudinal axis of the pressure vessel is greater than 10xc2x0. In a further aspect of the invention, the cold gas inflator has axial flow elbow to direct the stored gas out of the inflator in an axial direction. With the axial flow elbow, the stored gas does not flow along the longitudinal axis of the pressure vessel.